1. Field of the Invention
The present invention relates to an ink capable of forming a flourescent image which is suitably used for ink-jet recording, an ink cartridge employing the ink, and an ink-jet recording method and an ink-jet recording apparatus employing the ink.
2. Related Background Art
Hitherto, various compositions have been reported regarding an ink which employs a fluorescent dye containing a pyrene ring as the coloring material primarily for writing materials. For instance, Japanese Patent Application Laid-Open No. 6-73324 has proposed a fluorescent water-based ink for a ball-point pen which comprises a fluorescent dye of from 0.01 to 30%, triethanolamine of from 5 to 50%, a viscosity modifier composed of a high molecular compound, and water, and which has a solid content of from 15 to 60% in a dry state and a viscosity of from 50 to 2,000 cP.
Japanese Patent Application Laid-Open No. 59-43076 has proposed a yellow fluorescent ink for ink-jet recording which provides good properties with improved water- and light-fastnesses by adding a fluorescent whitening agent in an amount of from 1 to 5% to yellow ink.
The foregoing ink disclosed in Japanese Patent Application Laid-Open No. 6-73324, however, is required just to satisfy a desired coloring ability and a light fastness when it is used to produce an image of the single color applied onto a medium such as paper, and it is formulated as such.
Upon forming a fluorescent image by employing an ink-jet recording method, the ink used for producing the fluorescent image is required to provide the performance peculiar to the ink-jet recording method. To be more specific, the ink is required to exhibit various properties for ensuring stable high printing quality in the ink-jet recording, including an anti-clogging property to nozzles, stability in re-ejection property of ink after a printing pause, and a property for minimizing a chance of a whisker-like feathering which may occur when an image is printed on a recording medium such as paper, or of a color bleed in boundary portions of an image due to different color inks.
In addition, when producing a multi-color image by using the ink-jet recording method, a secondary color obtained by mixing two colors such as yellow, red, green, and blue and the like instead of using a single color, or even a tertiary color produced by adding black to the foregoing two colors may be printed. When printing an image of such mixed colors, the mixed-color image is required to show a good coloring ability and a light fastness. No fluorescent ink, however, has been available which can be suitably used for ink-jet recording and which is formulated with attention paid to the foregoing respects.